This application entitled: "Emergence of Co-occurring Depressive and Externalizing Problems: Phenomenology, Course, and Outcome" was written as a response to RFA: MH-01-002. The Principal Investigator is a new investigator, who has convened a team of experienced developmental psychologists and research methodologists. Mental illness is a significant public health problem that is common in children and adversely affects their development. According to the recently published Surgeon General's Report, "mental illnesses exact a staggering toll on millions of individuals, as well as on their families and communities, and our Nation as a whole." Critical to the Healthy People 2010 objective of reducing the prevalence of mental disorders among children and adolescents is a clearer understanding of the developmental processes underlying childhood psychopathology. For children who have mental disorders, co-occurrence of multiple disorders is more the rule than the exception. Yet very little is known about the differences in phenomenology, course, and outcome when disorders co-occur and when they do not. The proposed study is designed to identify developmental precursors, describe phenomenology, document developmental sequences, identify moderators and mediators of longitudinal course, and document functional outcomes in four groups of children. Study subjects will include children in three "vulnerable" groups: depressive, only; externalizing, only; and co-occurring depressive and externalizing; and a comparison group of children without these vulnerabilities. The study will be conducted in King County, Washington. Study subjects will be selected on the basis of school problem status and parent-reported internalizing and externalizing problems from among 6th grade students in the Seattle Public Schools. In-person structured interviews focusing on key study constructs will be conducted with children and their caregivers and teachers at Baseline and at 12 and 24-month follow-up, with telephone/mail interviews conducted at intervening points. To address study aims, longitudinal data will be analyzed using logistic regression, Cox proportional hazards, growth mixture models, and classification and regression tree (CART) methods. Understanding the nature of co-occurring psychopathology will have important implications for nosology, as well as for the development of effective prevention and treatment approaches. The availability of a diverse population of children, the collaborative relationship between the University of Washington and the Seattle Public School District, and the experienced team of researchers create excellent conditions to conduct a study that can specifically address the questions posed in this RFA.